1. Field of Invention
This disclosure relates to creating an output pulse of a circuit, and in particular to modulating the width of the output pulse of a circuit.
2. Description of Related Art
One of the limitations of providing greater resolution in current printer technology involves the width of electrical pulses that are used to generate data. Current printer technology produces pixels by providing a print engine with electrical pulses, where the size of the pixel is a function of the duration of the electrical pulse. Greater resolution for printed material can be obtained by providing data, for example sub-pixel data, at a higher frequency than the base frequency of the electrical pulses used by the print engine. By providing data at a higher frequency, the printer can print a fraction of a pixel instead of a whole pixel, obtaining higher resolution in the process.
In one technique, serial data is provided at a frequency higher than the base frequency of the print engine and uses the serial data of higher frequency to print one dot with a controlled grey-scale level. Providing this serial data, however, requires a pulse generation circuit with much higher resolution than the print engine resolution. Thus, if resolution of the printed material is to be increased by 16 times using the above method, then the serial data must be provided at a frequency 16 times the frequency of the print engine. Thus, if a print engine has a clock running at 30 MHz, then the serial data would need a clock running at 480 MHz. In many cases, this higher clock speed can be obtained only by using a cost-prohibitive integrated circuit (“IC”).
Another technique that is used to increase printer resolution involves the use of fixed delays to generate finely controlled pulse widths. One drawback of this approach is that it is not easy to obtain similar pixel modulation performance across a wide range of printer base resolution frequencies. For example, if the circuit is designed to generate 16 grey-scale levels with a base frequency of 1 MHz, the same circuit will only provide 8 grey-scale levels with a different printer of a base frequency of 30 MHz. Another drawback occurs because the delays are typically implemented with IC gate delays that tend to vary widely from IC to IC because of unavoidable process variations.
Accordingly, there is a need for a system and method for generating higher resolution printer images that can be used across a wide range of printer base frequencies.